Solar photovoltaic assemblies are typically connected in series to increase the voltage before inputting into an inverter, which generates an AC current to a power grid or for use by a device. Output current of the serial-connected photovoltaic assemblies is limited by the photovoltaic assembly with the lowest current, making acquire maximum energy from each photovoltaic assembly impossible.
Output voltage of the photovoltaic assembly varies in a wide range with the illumination conditions. At present, a typical inverter design may support a wide range of input voltages. Since conversion efficiency varies with input voltage, the overall conversion efficiency of the inverter is lower than that at an optimal voltage. Additionally, a significant input voltage variation may increase the stress of the components, thereby affecting reliability and lifetime of the inverter.
Also, maintenance for a serial-connected photovoltaic system is very difficult, since failure of any photovoltaic assembly may cause failure of a string of components, and determining the fault component is difficult and high cost.